The invention relates to a method for evaluating the course of the combustion chamber pressure and internal combustion engines.
It is known to ascertain the course of the combustion chamber pressures in the cylinders of an internal combustion engine with the aid of suitable sensors, and from this course to detect operating states of the engine and obtain trigger signals for controlling the engine. Typically, each cylinder of the engine is assigned a combustion chamber pressure sensor. A crankshaft sensor is also used, which furnishes an output signal that is representative for the crankshaft position. The two signals are evaluated jointly in the engine control unit. A camshaft sensor is no longer needed, since it is possible, especially after starting, to synchronize the crankshaft and camshaft position by linking the course of the combustion chamber pressure and the crankshaft sensor signal. A method in which the course of combustion chamber pressure is evaluated as a function of the crankshaft position, for the sake of cylinder detection and to generate signals required for ignition, is known from published, unexamined German Patent Application DE-OS 44 05 015. The cylinder detection and the detection of the crankshaft revolution in which the engine is located in a combustion cycle is performed in the known method by evaluating the pressure increase in a certain cylinder, for instance, and distinguishing between a pressure increase in the compression stroke and a pressure increase in the ensuing combustion. Since these values are different, the crankshaft revolution in which the engine is located can be ascertained. From this finding, control signals for the engine can be generated.
In the known method, an evaluation of the course of combustion chamber pressure to detect the valve control times, that is, in order to detect whether the outlet valve is opening or closing or whether the inlet valve is opening or closing, is not performed.